Helical recording systems have been employed in broadcast VTRs to achieve high data transmission rates. In particular, the increasing popularity of high image quality broadcasts such as high vision broadcasts and digital ground wave broadcasts has required increasingly higher data transmission rates. Helical recording systems are even employed in data storage systems such as DTF1 and DTF2 to achieve high data transmission rates.
Achieving high data transmission rates requires increasing the speed of drum rotation, developing high-output tapes, and the like. Decreasing the space between tape and head, that is, rendering the surface smooth, is an extremely effective method of achieving high output. However, when the space between tape and head is reduced, the abrasive present on the tape surface contacts the head with increased frequency, thus abrading the head. Further, even when the drum rotation rate is increased, the frequency of contact between head and abrasive increases, resulting in substantial wear on the head. Accordingly, it is important to design a recording and reproduction system so as to reduce head abrasion to achieve high data transmission rates.
Since the relative speed between the tape and the head is high in helical recording systems, stable contact between the tape and the head, known as secure head contact, is known to be extremely important. When there is a small gap between the drum and head, the tape is sometimes drawn into the gap as the drum rotates. When the tape is drawn into the gap between drum and head, the spacing loss between tape and head increases and output drops. In particular, when the drum rotation rate increases, the amount of tape drawn into the gap increases, spacing loss increases, and head contact deteriorates. Accordingly, a design ensuring head contact, specifically, the design of tape stiffness, has assumed even greater importance.
Methods such as increasing the drawing factor during film formation are known to effectively increase the Young's modulus in the width direction of the base to ensure head contact. As specific examples of increasing the Young's modulus in the width direction of the base, Japanese Unexamined Patent Publication (KOKAI) Showa Nos. 50-46303, 54-34206, 62-234233, 63-197643, and 63-212549, and Japanese Unexamined Patent Publication (KOKAI) Heisei Nos. 2-20924 and 4-49515 propose techniques employing polyethylene terephthalate (reinforced PET) or polyethylene-2,6-naphthalate (PEN) with a greater than normal Young's modulus in the width direction; aromatic polyamide (aramid); and compound polyester. However, even when these techniques are employed to adjust the stiffness to within what is considered to be the optimal region, there remains a need for better head contact.
It is an object of the present invention to provide a magnetic recording medium affording good head contact and high output in addition to excellent head abrasion characteristics acceptable to high data transmission rates.